Photocurable composition based on acid functional primary resinous mercaptans

Abstract

Acid functional primary thiols having no hydroxy substituents in the beta position, and also having aromatic backbones, can be combined with unsaturated resins to make aqueous base-developable, photoimaging compositions such as solder masks and resists.

What is claimed is: 
     
       1. A photoimageable composition developable in aqueous base comprising (i) an acid-functional thiol-functional resin having two or more primary aliphatic thiol groups having no hydroxy substituents in the beta positions with respect to the sulfur atom, and a thermally stable backbone with substantial aromatic, cyanurate or isocyanurate character, (ii) a polymerizable unsaturated resin and (iii) a photoinitiator. 
     
     
       2. The photoimageable composition of claim 1, wherein the thiol-functional resin is a derivative of an unsaturated Novolak resin. 
     
     
       3. The photoimageable composition of claim 1 wherein the thiol-functional resin is a derivative of an unsaturated cyanurate or an isocyanurate resin. 
     
     
       4. The photoimageable composition of claim 1 wherein the thiol-functional resin is a derivative of the group consisting of an allylated Novolak, cyanurate and isocyanurate resins. 
     
     
       5. The photoimageable composition of claim 4, wherein the thiol-functional resin is a derivative of tetraallylated Bisphenol A. 
     
     
       6. The photoimageable composition of claim 4, wherein the thiol-functional resin is a derivative of hexaallylated Bisphenol A. 
     
     
       7. The photoimageable composition of claim 4, wherein the thiol-functional resin is a derivative of a polyallylated phenol novolak resin. 
     
     
       8. The photoimageable composition of claim 1 wherein the thiol-functional resin is the hydrolyzed a reaction product of an unsaturated Novolak resin and a mixture of thiolacetic acid and β-mercaptopropionic acid. 
     
     
       9. The photoimageable composition of claim 1 wherein the acid-functional, thiol-functional resin is a reaction product of a thiol-functional phenol or cresol Novolak resin and a cyclic anhydride selected from the group consisting of maleic, succinic, trimellitic, phthalic, tetrahydrophthalic, hexahydrophthalic anhydride and blends thereof. 
     
     
       10. The photoimageable composition of claim 1, wherein the thiol-functional resin is a reaction product of an unsaturated resin having a backbone selected from the group consisting of aromatic, cyanurate, and isocyanurate oligomers and blends thereof, and a group capable of inserting an acid-functional moiety selected from the group consisting of cyclic anhydrides and a mixture of thiolacetic acid and β-mercaptopropionic acid. 
     
     
       11. The photoimageable composition of claim 1, further comprising one or more photosensitizers, inhibitors, pigments, dyes, fillers, stabilizers, solvents, adhesion promoters, thiol-containing oligomers, epoxy resins, or rheology aids. 
     
     
       12. The photoimageable composition of any one of claim 1, or 11, wherein the polymerizable unsaturated resin is substantially ester-free. 
     
     
       13. The photoimageable composition of any one of claim 1, or 11, wherein the polymerizable unsaturated resin has two or more unsaturated groups. 
     
     
       14. The photoimageable composition of any one of claim 1, or 11, wherein the polymerizable unsaturated resin has substantial aromatic, cyanurate, or isocyanurate character. 
     
     
       15. A method of making a photoimageable composition developable in aqueous base, the steps comprising a. adding thiolacetic acid and 8-mercaptopropionic acid to an unsaturated compound that is totally ester-free, and has a thermally stable backbone with substantial aromatic, cyanurate or isocyanurate character, under conditions suitable to induce free radical addition of the mercaptan groups of the thiolacetic acid and B-mercaptopropionic acid to the allyl groups of the unsaturated compound to produce a reaction product,   b. hydrolyzing the reaction product, and   c. blending the reaction product with a polymerizable unsaturated resin and a photoinitiator.   
     
     
       16. The method of claim 15 wherein the step of hydrolyzing the reaction product is performed under basic conditions. 
     
     
       17. The method of claim 15, wherein the step of hydrolyzing the reaction product is performed under acidic conditions. 
     
     
       18. The method of claim 15, wherein the backbone of the unsaturated compound is selected from the group consisting of novolak, cyanurate and isocyanurate resins. 
     
     
       19. The method of claim 18, wherein the unsaturated compound is a phenol novolak resin. 
     
     
       20. The method of claim 18, wherein the unsaturated phenol novolak resin is a tetraallyl derivative of Bisphenol A. 
     
     
       21. The method of claim 18, wherein the unsaturated phenol novolak resin is a hexaallyl derivative of Bisphenol A. 
     
     
       22. A method of making a photoimageable composition developable in aqueous base, the steps comprising a. adding a cyclic anhydride to a totally ester-free, thiol-functional resin having two or more primary aliphatic thiol groups having no hydroxy substituents in the beta positions with respect to the sulfur atom, and a thermally stable backbone with substantial aromatic, cyanurate or isocyanurate character under conditions suitable to induce reaction of a portion of the thiol functionality of the resin with the anhydride, thereby producing a reaction product and,   b. blending the reaction product with a polymerizable unsaturated resin and a photoinitiator.   
     
     
       23. The method of claim 22, wherein the thiol-functional resin is a derivative of a phenol novolak resin. 
     
     
       24. The method of claim 23, wherein the phenol novolak resin is a tetraallyl derivative of Bisphenol A. 
     
     
       25. The method of claim 23, wherein the phenol novolak resin is a hexaallyl derivative of Bisphenol A. 
     
     
       26. The method of claim 22, wherein the anhydride is selected from the group consisting of maleic, succinic, trimellitic, phthalic, tetrahydrophthalic, and hexahydrophthalic anhydride. 
     
     
       27. The method of claim 22, wherein the anhydride is trimellitic anhydride. 
     
     
       28. The method of claim 22, wherein the anhydride is phthalic anhydride. 
     
     
       29. The method of claim 22, wherein the anhydride is hexahydrophthalic anhydride.